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            <h2 class="title"><a id="enabletxn"></a>Chapter 2. Enabling Transactions</h2>
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      <div class="toc">
        <p>
          <b>Table of Contents</b>
        </p>
        <dl>
          <dt>
            <span class="sect1">
              <a href="enabletxn.html#envopen">Opening a Transactional Environment and
            
            <span>Store or Database</span>
            
        </a>
            </span>
          </dt>
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      <p>
        In order to use transactions with your application, you must turn them
        on. To do this you must: 
  </p>
      <div class="itemizedlist">
        <ul type="disc">
          <li>
            <p>
            Turn on transactions for your environment.

            <span>
            You do this by using the
            <code class="methodname">EnvironmentConfig.setTransactional()</code>
            method<span>, or by using the 
                <code class="literal">je.env.isTransactional</code> 
                <code class="filename">je.properties</code> parameter</span>.
            </span>

            

            
        </p>
          </li>
          <li>
            <p>
                If you are using the DPL, transaction-enable your stores.
                You do this by using the 
                <code class="methodname">StoreConfig.setTransactional() method.</code>
            </p>
          </li>
          <li>
            <p>
            <span>
                    Transaction-enable your databases. 
            </span>
            <span>
                    If you are using the base API, transaction-enable your databases. 
            </span>
            You do this by
            <span>
                using the
                <code class="methodname">DatabaseConfig.setTransactional()</code>
                method, and then opening the database from within a transaction.
            </span>

            
            

             <span>
             Note that the common practice is for auto commit to be used to
             transaction-protect the database open. To use auto-commit, you
             must still enable transactions as described here, but you do
             not have to explicitly use a transaction when you open your
             database. An example of this is given in the next section.
             </span>
        </p>
          </li>
        </ul>
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      <div class="sect1" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h2 class="title" style="clear: both"><a id="envopen"></a>Opening a Transactional Environment and
            
            <span>Store or Database</span>
            
        </h2>
            </div>
          </div>
        </div>
        <p>
            To enable transactions for your environment, you must initialize the
            transactional subsystem. For example, do this with the DPL:
        </p>
        <pre class="programlisting">package persist.txn;

import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;

import com.sleepycat.persist.EntityStore;
import com.sleepycat.persist.StoreConfig;

import java.io.File;

...

Environment myEnv = null;
EntityStore myStore = null;
try {
    EnvironmentConfig myEnvConfig = new EnvironmentConfig();
    StoreConfig storeConfig = new StoreConfig();

    myEnvConfig.setTransactional(true);
    storeConfig.setTransactional(true);

    myEnv = new Environment(new File("/my/env/home"),
                              myEnvConfig);
    myStore = new EntityStore(myEnv, "EntityStore", storeConfig);

} catch (DatabaseException de) {
    // Exception handling goes here
}</pre>
        <p>
            And when using the base API:
    </p>
        <pre class="programlisting">package je.txn;

import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;

import java.io.File;

...

Environment myEnv = null;
try {
    EnvironmentConfig myEnvConfig = new EnvironmentConfig();
    myEnvConfig.setTransactional(true);

    myEnv = new Environment(new File("/my/env/home"),
                              myEnvConfig);

} catch (DatabaseException de) {
    // Exception handling goes here
}</pre>
        <p>
        You then create and open your database(s) as you would for a non-transactional system.
        

        <span>
            The only difference is that you must set
                <code class="methodname">DatabaseConfig.setTransactional()</code>
            to <code class="literal">true</code>. Note that your database open must be
            transactional-protected. However, if you do not give the 
            <code class="methodname">openDatabase()</code> method a transaction handle,
            then the open is automatically protected using auto commit.
            Typically auto commit is used for this purpose.
            For example:
            
        </span>
    </p>
        <pre class="programlisting">package je.txn;

<strong class="userinput"><code>import com.sleepycat.je.Database;
import com.sleepycat.je.DatabaseConfig;</code></strong>
import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;

import java.io.File;

...

<strong class="userinput"><code>Database myDatabase = null;</code></strong>
Environment myEnv = null;
try {
    EnvironmentConfig myEnvConfig = new EnvironmentConfig();
    myEnvConfig.setTransactional(true);
    myEnv = new Environment(new File("/my/env/home"),
                              myEnvConfig);

    <strong class="userinput"><code>// Open the database. Create it if it does not already exist.
    DatabaseConfig dbConfig = new DatabaseConfig();
    dbConfig.setTransactional(true);
    myDatabase = myEnv.openDatabase(null,
                                    "sampleDatabase",
                                    dbConfig);</code></strong>

} catch (DatabaseException de) {
    // Exception handling goes here
}

</pre>
        <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
          <h3 class="title">Note</h3>
          <p>
                Never close a database <span> or
                        store </span> that has active transactions. Make sure
            all transactions are resolved (either committed or aborted)
            before closing the database.
        </p>
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